As is well known to those having skill in the art, monocrystalline silicon carbide is particularly well suited for use in semiconductor devices, such as integrated circuit semiconductor devices and power semiconductor devices. Integrated circuit semiconductor devices typically include many active devices such as transistors in a single semiconductor substrate. Power semiconductor devices, which may be integrated circuit devices, are semiconductor devices which carry large currents and support high voltages.
Silicon carbide has a wide bandgap, a high melting point, a low dielectric constant, a high breakdown field strength, a high thermal conductivity and a high saturated electron drift velocity compared to silicon, which is the most commonly used semiconductor material. These characteristics allow silicon carbide microelectronic devices to operate at higher temperatures and higher power levels than conventional silicon based devices. In addition to the above advantages, silicon carbide power devices can operate with lower specific on-resistance than conventional silicon power devices. Some of the advantages of using silicon carbide for forming power semiconductor devices are described in articles by K. Shenai, R. S. Scott, and inventor B. J. Baliga, entitled Optimum Semiconductors for High-Power Electronics, IEEE Transactions on Electron Devices, Vol. 36, No. 9, pp. 1811-1823 (1989); and by M. Bhatnagar and inventor B. J. Baliga entitled Analysis of Silicon Carbide Power Device Performance, ISPSD '91, Abstr. 8.3, pp 176-180 (1991).
Many of the processes for forming microelectronic devices require the formation of insulating regions, such as oxides, that act as masks for device processing, perform the function of electrically isolating one or more regions of a semiconductor device from one another, and insulate adjacent semiconductor devices on a semiconductor substrate from each other. Conventional techniques for forming insulating regions on silicon include thermal oxidation, low pressure chemical vapor deposition (LPCVD) and plasma-assisted deposition. As will be understood by one skilled in the art, thermal oxidation is probably the most common technique used to grow high quality oxides, such as those made of SiO.sub.2, on silicon substrates.
In addition to the numerous techniques for forming oxides on silicon, thermal oxidation of silicon carbide has also been investigated. For example, in an article by J. W. Bumgarner, H. S. Kong, H. J. Kim, J. W. Palmour, J. A. Edmond, J. T. Glass, and R. F. Davis, entitled Monocrystalline .beta.-SiC Semiconductor Thin Films: Epitaxial Growth, Doping and FET Device Development, 1988 Proc. 38th Electronics Components Conf., pp. 342-349, a depletion-mode MOSFET including a 430.ANG. thermally grown gate oxide was produced. The gate oxide was grown at a temperature of 1273 degrees Centigrade (1473K) and required ninety (90) minutes in a flowing O.sub.2 ambient. Similarly, in an article by R. F Davis, entitled Epitaxial Growth and Doping of and Device Development in Monocrystalline .beta.-SiC Semiconductor Thin Films, Thin Solid Films, vol. 181, pp. 1-15, (1989), a 500.ANG. gate oxide was obtained after oxidizing P-type .beta.-SiC samples at 1273 degrees Centigrade (1473K) for thirty-six (36) minutes.
Notwithstanding these attempts at growing thin gate oxide layers on silicon carbide substrates, however, the formation of substantially thick oxides on the order of 5000-10,000.ANG., using growth techniques at temperatures below 1200 degrees Centigrade (1473K), has not heretofore been achieved. Such thick oxides are used, for example, to electrically insulate regions of a device using oxide layers and for electrically insulating adjacent devices from each other using oxide-filled trenches. Thick oxides are particularly important for power devices to prevent electric arcing or field oxide breakdown, between regions of a device or between adjacent devices, when such devices are operated in the presence of high electric fields and at high current levels.